The present invention relates generally to using ultrasound for delivery of drugs from microspheres. Diagnostic medical ultrasound imaging has been used to image microspheres. The microspheres are imaged using linear, nonlinear or stochastic responses of the microspheres to varying intensities of acoustic pressure. In addition to imaging microspheres, medical diagnostic ultrasound systems destroy microspheres with acoustic energy. The destruction of the microspheres is optimized such that subsequent imaging shows an inflow or wash-in of new microspheres into the image region or provides a loss of correlation.
The destruction of microspheres may provide more efficient delivery of drugs. In xe2x80x9cEchocardiographic Destruction Of Albumin Directs Gene Delivery To The Myocardiumxe2x80x9d, Circulation, June 2,000, R. Shohet, Paul Grayburn and others delivered an adenoviral transgene to a rat myocardium using ultrasound medicated microbubble destruction. The microspheres used comprised albumin coated microbubbles. A tenfold increase in activity of the drug was produced.
The present invention is defined by the following claims, and nothing in this section should be taken as a limitation on those claims. By way of introduction, the preferred embodiment described below includes a method and system for delivering drugs carried by microspheres. A medical diagnostic ultrasound system is used to destroy microspheres, releasing drugs in a specific localized area or at a specific time.
In one aspect, a region of interest that is a subset of an imaged area is identified for destroying drug-carrying microspheres. The transmit beamformer is configured to transmit acoustic energy for destroying microspheres within that area while minimizing the destruction of microspheres outside of the region of interest. In a second aspect, a multidimensional transducer array provides elevation focusing for accurately destroying microspheres in a specific region while minimizing the destruction of microspheres outside that region. In a third aspect, a trigger, such as a trigger responsive to a heart or breathing cycle, determines when microspheres are destroyed, providing delivery of drugs at the most opportune time in the cycle.
Other aspects and advantages of the invention are discussed below in conjunction with preferred embodiments.